Combining different libraries with their respective memory management and error handling ideas is one of my biggest issues with C++. You have to keep so many things in mind to use every API according to its own peculiar rules. One slip of the mind and you're in big trouble.

Also, getting all those libraries to compile with a particular compiler/stdlib combination is a big hassle. Things break in non obvious ways because of weird implicit template instantiations that are basically untestable by the creator of the library.

These types of integration issues are never going to go away and therefore C++ will occupy a stable niche forever but will never become mainstream for application development again, regardless of any language improvements.